The present invention relates to methods and compositions for modulating an immune response. The invention includes the use of the protein OX-2 to suppress an immune response and to prevent fetal loss.
The immune system protects the body from infectious agents and disease and is critical to our survival. However, in certain instances, the immune system can be the cause of illness. One example is in autoimmune disease wherein the immune system attacks its own host tissues, in many instances causing debilitating illness and sometimes resulting in death. Examples of autoimmune diseases include multiple sclerosis, type 1 insulin-dependent diabetes mellitus, lupus erythematosus and arthritis. A second example where the immune system can cause illness is during tissue or organ transplantation. Except in the cases of genetically identical animals, such as monozygotic twins, tissue and organ transplants are rejected by the recipient""s immune system as foreign. The immune reaction against transplants is even more pronounced in transplantation across species or xenotransplantation. A third example where the immune system harms the host is during an allergic reaction where the immune system is activated by a generally innocuous antigen causing inflammation and in some cases tissue damage.
In order to inhibit the detrimental immune reactions during transplantation, autoimmune disease and allergic reactions, immunosuppressive drugs (such as cyclosporin A, tacrolimas, and corticosteroids) or antibody therapies (such as anti-T cell antibodies) are generally administered. Unfortunately, these non-specific modes of immunosuppression generally have undesirable side effects. For example, cyclosporin may cause decreased renal function, hypertension, toxicity and it must be administered for the life of the patient. Corticosteroids may cause decreased resistance to infection, painful arthritis, osteoporosis and cataracts. The anti-T cell antibodies may cause fever, hypertension, diarrhea or sterile meningitis and are quite expensive.
In view of the problems associated with immunosuppression, there has been an interest in developing methods or therapies that induce unresponsiveness or tolerance in the host to a transplant, to xe2x80x9cselfxe2x80x9d tissues in autoimmune disease and to harmless antigens associated with allergies. The inventor has been studying the mechanisms involved in transplant rejection and has developed methods for inducing a state of antigen-specific immunological tolerance in transplantation. In particular, in animal allograft models, the inventor has demonstrated that graft survival can been increased if the recipient animal is given a pre-transplant infusion via the portal vein of irradiated spleen cells from the donor animal. In contrast, a pre-transplant infusion via the tail vein does not prolong graft survival.
Understanding the molecular mechanisms involved in the induction of tolerance following portal-venous (pv) immunization may lead to the development of methods of inducing immune tolerance that may be useful in transplant, autoimmune disease and allergies.
Genes that show an increase in expression following portal venous immunization have been identified. One of the genes isolated encodes OX-2, a molecule with previously unknown function belonging to the Ig superfamily. The OX-2 molecule is also generally referred to as CD200 in the current literature. The inventors have shown that administering antibodies to OX-2 inhibited the graft survival generally seen following pre-transplant pv immunization. The inventors have also shown that there is a negative association between levels of OX-2 and risk of fetal loss. In particular, the inventors have shown administering OX-2 reduced fetal loss rates while inhibiting OX-2 reversed the effect. The inventors have further shown that OX-2 inhibits cytotoxic cells and IL-2 production and induces IL-4 production. All of these results demonstrate that OX-2 is involved in immune suppression.
Consequently, broadly stated, the present invention provides a method of suppressing an immune system comprising administering an effective amount of an OX-2 protein or a nucleic acid sequence encoding an OX-2 protein to an animal in need of such treatment.
In one embodiment, the present invention provides a method of preventing or inhibiting fetal loss comprising administering an effective amount of an OX-2 protein or a nucleic acid sequence encoding an OX-2 protein to an animal in need thereof.
The invention also includes pharmaceutical compositions containing OX-2 proteins or nucleic acids encoding OX-2 proteins for use in inducing tolerance in transplantation or autoimmune disease.
As stated above, OX-2 can be used to induce immune suppression. Consequently, inhibiting OX-2 may also be useful in preventing immune suppression.
Therefore, in another aspect, the present invention provides a method of preventing immune suppression comprising administering an effective amount of an agent that inhibits OX-2 to an animal in need thereof. In a preferred embodiment the OX-2 inhibitor is an antibody that binds OX-2 or an antisense oligonucleotide that inhibits the expression of OX-2.
In one embodiment, the present invention provides a method of inducing fetal loss comprising administering an effective amount of an agent that inhibits OX-2 to an animal in need thereof.
The invention also includes pharmaceutical compositions containing an OX-2 inhibitor for use in inducing or augmenting an immune response.
Other features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples while indicating preferred embodiments of the invention are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.